docs: def split_header(fp):
          """
          Read file pointer and return pair of lines lists:
          first - header, second - the rest.
          """
          body_start, header_ended = 0, False
          lines = []
          for line in fp:
              if line.startswith('#') and not header_ended:
                  # Header text
                  body_start += 1
              else:
                  header_ended = True
              lines.append(line)
          return lines[:body_start], lines[body_start:]